1. Field of the Invention
The invention relates to a semiconductor device, particularly, a chip size package type semiconductor device having a light receiving element.
2. Description of the Related Art
A CSP (chip size package) has received attention in recent years as a new packaging technology. The CSP is a small package having about the same outside dimensions as those of a semiconductor die packaged in it.
A BGA (ball grid array) type semiconductor device has been known as a type of the CSP. In the BGA type semiconductor device, a plurality of ball-shaped conductive terminals made of metal such as solder is arrayed on one surface of a package and is electrically connected to a semiconductor die mounted on the other surface of the package.
When the BGA type semiconductor device is mounted on electronic equipment, the semiconductor die is electrically connected to an external circuit on a printed board by bonding the conductive terminals to wiring patterns on the printed board.
Such a BGA type semiconductor device has advantages in providing a large number of conductive terminals and in reducing a size over the other CSP type semiconductor devices such as an SOP (small outline package) and a QFP (quad flat Package), which have lead pins protruding from their sides. Therefore, the BGA type semiconductor device has a wide field of application.
FIG. 6A is a schematic cross-sectional view of a conventional BGA type semiconductor device having a light receiving element. A light receiving element 101 such as a CCD (charge coupled device) image sensor or a CMOS image sensor is provided on a front surface of a semiconductor substrate 100 made of silicon (Si) or the like, and a pad electrode 102 is further formed with a first insulation film 103 interposed therebetween. A light transparent substrate 104 made of, for example, glass, quartz or the like is further attached on the front surface of the semiconductor substrate 100 with a resin layer 105 made of epoxy resin or the like interposed therebetween. Furthermore, a second insulation film 106 made of a silicon oxide film or a silicon nitride film is formed on a side surface and a back surface of the semiconductor substrate 100.
Furthermore, a wiring layer 107 electrically connected to the pad electrode 102 is formed on the second insulation film 106 from the front surface to the back surface along the side surface of the semiconductor substrate 100. A protection layer 108 made of a solder resist or the like is formed covering the second insulation film 106 and the wiring layer 107. An opening is formed in a predetermined region of the protection layer 108 on the wiring layer 107, and a ball-shaped conductive terminal 109 is formed being electrically connected to the wiring layer 107 through this opening. The relevant technology is disclosed in Japanese Patent Application Publication No. 2002-512436.
In this conventional BGA type semiconductor device, however, when an infrared ray is used, there can be a case where an infrared ray passing through the light transparent substrate 104 also passes through the semiconductor substrate 100 and reaches the wiring layer 107 formed on the back surface of the semiconductor substrate 100, as shown by an arrow in FIG. 6A. Then, this infrared ray is reflected by the wiring layer 107 to travel upward (toward the light receiving element 101) and the light receiving element 101 receives the reflected light, thereby causing a problem that patterns 111 of the conductive terminal 109 and the wiring layer 107 are reflected on an output image 110 as shown in FIG. 6B.